The geometric mass \(\mathfrak {m}\)  for non-static structure could be
computed via Misner-Sharp framework as[1]}
\(\mathfrak {m}(t,r)=\left(1+\frac{\dot{\dot{C}}^{2}}{A^{2}}-\frac{C^{\prime 2}}{B^{2}}\right)\frac{C}{2}.\) 
